if he is invading at any moment before level 4 he is auto-losing his lane. You would think jg understood xp the most, but they normally do the least. Literally just by coming to get first blood and help you get your greedy fucking scuttle, I normally lose lane from that because the enemy collects 7 minions(150gold, but more importantly 200 XP), and the fact I get first blood ends up meaning nothing against it, in the literal seconds it takes me to flash, shunpo, ignite, kill, shunpo back to lane, I lose it.
Now imagine when I get don't even a kill, and you steal 70-120 of my xp with your 'drive by' level ups that only let him get 6 first on me, and destroy every advantage I've tried to create. This is why I complain when he is shoving me, a situation where I am already behind, and half the time I now just expect jg to attempt to clear the wave, and officially make me a support for the rest of the game. Hell fucking yes the point is to be csing, it's one thing if the mid doesn't call mia out for you, but if he tells you to stop PvEing a rock, and to fucking not die to an invade that is wasting the enemies time if you just LEAVE, then you will win the game. But the idea you need to sit at blue buff and fucking die for it is a joke, especially when you have every imaginably ability to solo it later for free completely uncontested. The Blue buff itself is only worth 1 wave of minions itself and so best case scenario he goes EVEN for XP and gains a blue buff and loses 50 gold, while the jg gains nothing. Or maybe the JG smites the blue buff his mid laner helped him invade for, because all jg are greedy fucks, and then mid just loses the fucking lane for nothing by invading you.